The manufacture and use of synthetic laundry detergents containing mixtures of nonionic and anionic surfactants has been documented in the patent literature. See, for example, Bonaparte et al. U.S. Pat. No. 3,920,586 granted Nov. 18, 1975. Moreover, the use of ethoxylated alcohols (referred to herein, for convenience, by the "EA" acronym) as the nonionic constituent of such mixtures, and ethoxy sulfates (referred to herein by the "ES" acronym) as the anionic constituent of such mixtures has also been described (see the aforesaid Bonaparte patent, column 2, lines 32-37; column 3, lines 17-28; column 9, lines 30-45; and column 9, line 67 column 10, line 20).
Dry blended laundry detergents containing such EA/ES or other nonionic/anionic surfactant systems are further described, for example, in Winston et al. U.S. application Ser. No. 65,203, entitled "METHOD OF PREPARING DRY BLENDED LAUNDRY DETERGENT", filed on Aug. 9, 1979, now U.S. Pat. No. 4,265,790 granted on May 5, 1981. In the past, however, when for cost purposes EA's have been utilized as the nonionic constituent of such surfactant systems, the sudsing characteristics of the resulting dry blended detergent formulations have been impaired. Moreover, the use of EA/ES surfactant systems in dry blended detergent powders has been said to interfere with the processing characteristics thereof. Various efforts have been made to improve such processing characteristics. See, for example, Kowalchuk U.S. Pat. No. 4,137,197 granted Jan. 30, 1979, and U.S. Pat. No. 4,162,994 granted Jul. 31, 1979.
It has also been suggested in the patent literature that EA/ES mixtures useful in detergent compositions may be prepared by the direct sulfation of various EA materials. See, for example, Roele U.S. Pat. No. 3,309,392 granted Mar. 14, 1967, and Harris U.S. Pat. No. 3,959,186 granted May 26, 1976. The Roele patent describes a two-stage, gas phase reaction for the sulfation of EA's having at least 8 carbon atoms with sulfur trioxide/inert gas mixtures. The final products, which are said to be useful as detergents, wetting agents or the like, are sulfated with conversions ranging from 87 to 97%.
The Harris patent, on the other hand, describes the sequential partial sulfation of, first, a highly ethoxylated EA (incorporating from 8 to 25 moles of ethoxylate per mole of the alcohol) and, thereafter, a less ethoxylated compound (incorporating from 2 to 12 moles of ethoxylate per mole of alcohol, but at least 4 ethoxylate groups per mole less than the EA first sulfated). Harris further discloses that, after neutralization of the partial sulfate mixture thus produced, the resulting product may contribute both detergent and builder properties to dry detergent formulations. Detergents incorporating the same are said to be capable of dispersing lime soap and to possess satisfactory washing characteristics as compared with other commercial dry powder detergents.
It is among the objects of the present invention to provide an improved process for the preparation of mixed EA/ES surfactants, which process may be efficiently and inexpensively carried out. A further object is to provide such surfactants, and detergents incorporating the same, which exhibit the detergency (cleaning) and esthetic (whiteness) characteristics required of commercial laundry detergents and which, moreover, have substantially improved sudsing characteristics.
These and other objects and advantages will be apparent from the following detailed description, taken in connection with the accompanying drawing partially illustrating the compositions of the neutralized, partially sulfated EA/ES surfactants of the present invention.